Control of p53 multimerization by Ubc13 is JNK-regulated

Abstract

The p53 tumor suppressor protein is a key regulator of cellular proliferation and survival whose function is tightly regulated at the levels of transcription and protein stability. Here, we unveil the fine control of p53 on translationally active polysomes. We have previously reported that Ubc13, an E2 ubiquitin-conjugating enzyme, directly regulates p53 localization and transcriptional activity. We now demonstrate that the association of p53 and Ubc13 on polysomes requires ongoing translation and results in p53 ubiquitination that interferes with its tetramerization. JNK phosphorylation of p53 at Threonine 81 occurring on polysomes is required for the dissociation of Ubc13 from p53, leading to p53 multimerization and transcriptional activation. Inhibition of JNK activity or expression of a nonphosphorylatable mutant of p53 maintains an Ubc13-p53 complex that inhibits p53 multimerization. Our findings reveal a layer in the regulation of p53 multimerization that requires the concerted action of JNK and Ubc13 on polysome-bound p53.polysomes ͉ ubiquitin

Structural and Functional Comparison of the RING Domains of Two p53 E3 Ligases, Mdm2 and Pirh2

“…The effects of UBE2A/B in p53 monoubiquitylation have been reported and are implicated in regulating DNA damage response, p53 activity, and localization (54). UBE2N also has been shown to promote Lys 63 -linked p53 ubiquitylation, which attenuates Mdm2-mediated p53 polyubiquitylation when UBE2N is overexpressed in the cell (55,56). The function of UBE2Q proteins is not clear, and their role in Mdm2-mediated p53 ubiquitylation therefore warrants further investigation.…”

Search for Inhibitors of the Ubiquitin–Proteasome System from Natural Sources for Cancer Therapy

“…The Ubc13-Uev1A heterodimer is capable of binding to p53 bound to the polysome and catalyzes the K63-polyubiquitination of p53, which results in the inhibition of the tetramer formation. 34) Since the knockdown of Ubc13 was previously reported to increase p53 transcriptional activity, 35) we speculated that an inhibitor of the Ubc13-Uev1A interaction may induce the activation of p53 transcriptional activity and function as an anticancer agent. In our screening, 36) inhibition of the Ubc13-Uev1A interaction was tested in enzyme-linked immunosorbent assay (ELISA) using purified recombinant Ubc13 and FLAG-Uev1A proteins and a primary anti-FLAG antibody.…”

“…7) as a ubiquitin E1-specific inhibitor (IC 50 value, 50 µM). 29) In the course of the continuing search for E1 inhibitors, we next isolated five new alkaloids, hyrtioreticulines A-E 30) (35)(36)(37)(38)(39), together with one known alkaloid, hyrtioerectine B (40) (Fig. 7).…”

Zebrafish Mms2 promotes K63-linked polyubiquitination and is involved in p53-mediated DNA-damage response

“…Another reported involvement of Ubc13 in DNA-damage response is its negative regulation of p53 transcriptional activity in mammalian cells; this regulation is diminished upon DNA damage, allowing p53 activation [34]. This appears to be achieved through the direct association between Ubc13 and p53 on polysomes that results in p53 polyubiquitination and interference with its tetramerization [56]. In vitro studies suggest that both Mms2 and Uev1A can be potential cofactors and that Ubc13 requires K63 of Ub to stabilize p53 [34].…”